Midterm 1 Review Flashcards by Nahyeon Lee

over the course of brewing, what happens to the specific gravity?

makes a descending hill shape, much like what i’d like to sled down (dashed line)

decreases because density density of sugar is greater than EtOH, and sugar is being converted to EtOH

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over the course of brewing, what happens to the fusel alcohol content?

it increases because saccharomyces will always make it, just in lower concentrations than etoh. eventually the curve levels off when sugar is depleted.

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over the course of brewing, what happens to the temperature?

the temperature increases then decreases due. the respiration of the growing yeast causes the increase and then the temperature needs to be cooled to 20-22C otherwise more fusel alcohols will be produced.

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over the course of brewing, what happens to pH?

pH decreases to about 4ish due to the consumption of free amino nitrogen and conversion to organic acids and excreted protons. a bit too steep for me to want to sled down :0

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over the course of brewing, what happens to ester content?

it increases due to the esterification of ethanol; mirrors the production of alchol

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AAB can have a _____ growth curve

diauxic

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why do some AAB exhibit a diauxic growth curve?

the original log phase is due to oxidation ethanol to acetic acid. these AABs can oxidize acetic acid via TCA cycle, which is responsible for the second growth phase.

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if the starting concentration of ethanol is above ___%, the diauxic growth curve does not occur because _____ _____ concentration is too high.

3%; acetic acid

too much acetic acid kills cells

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what are some multi-organism fermentations?

sake
fukuyama pot vinegar
kefir

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what is the role of koji in production of pot vinegar?

converts starch to sugars for LAB and yeast to metabolize first, then they die off when AAB become more prominent at the surface

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why are pectinolytic microbes required during coffee fermentation?

enables removal of cherry from the bean

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why is komagataeibacter sp and not acetobacter used in industrial vinegar

koma is better capable of handling the higher concentrations of acetic acid >15%

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why are LAB and not AAB used for dairy fermentations

our primary fermentable sugar is lactose

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what type of organism is used for rind formation on surface ripened cheese? LAB, AAB, or mold?

mold

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Most yogurt cultures have approximately equal numbers of what two organisms?

streptococcus thermophilus and lactococcus bulgarius

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what is the common species succession in vegetable fermentation?

1) leuconostoc
2) lactobacillus plantarum
3) lactobacillus brevis

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why are coffee beans fermented?

to remove coffee cherry

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why are cocoa beans fermented?

to remove pulp, develop flavors, reduce bitterness, and BEAN DEATH

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why are campden crush tablets added to wine must?

kills AAB and natural flora, dechlorinates and acts as an antioxidant

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why are coffee beans fermented?

to remove coffee cherry/mucilaginous pulp

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why are campden crush tablets added to wine must?

kills AAB and natural flora, dechlorinates and acts as an antioxidant

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why is an air lock required when making wine?

provide anaerobic environment; protect against AAB; yeasts are more efficient with alcohol production in anaerobic environment

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why are needles used to puncture blue cheese during ripening process?

molds on the inside need to exchange gas to grow

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why is bean death important to the chocolate making process

if beans are alive, they’ll undesirably utilize the fermentable sugars

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why are hops added?

flavor development

why is yogurt fermentation generally carried out at 42C?

Streptococcus thermophilus and lactobacillus bulgaricus have different optimal temps. 42 is a compromise between the two.

why is citric acid in milk important for the flavor development in cheese?

citric acid can be converted to acetaldehyde and diacetyl aka the desired flavors

why is lactic acid fermentation sometimes required for finishing wine?

(malo) lactic fermentation imparts a buttery flavor. Oenococcus oeni ex) chardonnay

what is the role of rennet in cheese production?

enables curding

what roles does casein have in the textural development of cheese curds?

caseins make up 80% of milk's proteins. cheese is made by the coagulation of casein, which happens when they are converted to a nonpolar form to separate from water and entrap fat and minerals in the process. the more fat that is trapped, the stronger the curd. the casein matrix influences the cheese's ability to expel whey.

what roles does casein have in the textural development of cheese curds?

interaction of between acid destabilized k-casein and denatured whey

what does L. bulgaricus produce for S. thermophilus in yogurt fermentations?

peptides/amino acids

what biochemical is the most important contributor to taste in yogurt?

acetaldehyde

what is Nata de Coco composed of?

cellulose made by AAB on the surface of coconut water

what's special about civit coffee?

it's an intestinal fermentation

in the 1980s, what was special about activia yogurt?

has probiotic (bifidobacteria)

what are some differences between commercially sold sauerkraut and the sauerkraut you produced as part of this class?

``` commercial: - sold hermetically sealed and sterile - pasteurization partially cooks and softens - adds wine and spices Ours: - crunchier ```

is sugar added to grape must prior to wine fermentation?

nope

are all store-bought pickles fermented?

what types of olives are treated with lye prior to fermentation?

green

what's the difference between pH and titratable acid

note: organic food acids tend to be partially ionized, unlike strong acids titratable acid (aka total acidity): measures the total acid concentration in a food pH is the measure of H+ present

why do gram-negative bacteria tend to die during the first few days of LAB mediated fermentation reactions?

LA can diffuse in more easily inside the cell where it dissociates and kills

why do bacteriophages cause more of a problem for dairy fermentation than veggie ferments?

- dairy relies more heavily on a single strain while veggie relies on many. a bacteriophage can cause a dead vat with dairy, which is less likely to happen with vegetables due to the backup strains.

why is it important to start an AAB fermentation to produce vinegar with a starting ethanol concentration above 3%?

avoid overoxidation

how to AA resist being killed by acetic acid?

overoxidation, acetic acid pumps, general stress proteins, decreased surface area for lipophilic passive transport

if white mold forms on the surface of your wine, what should you do?

throw it out

what media do you use to differentiate homo/heterofermentative LAB?

HHD

what is a great media for isolating Listeria from mixed microbial communities?

PALCAM

what type of media is used to support the growth of lactobacilli?

ADPA, MRS

What is OGYE media used for

yeast

SCOBY = ?

symbiotic culture of bacteria and yeast

HHD = ?

hetero and homo differentiation

AAB = ?

acetic acid bacteria

what's the purpose of a Woronin body? a) block septum between hyphae to keep damage from spreading to additional cells b) act as a spore that is produced asexually by A. oryzae fungi c) promote fungal growth by activating tip extension d) participate in cyclic secretion of amylases e) critical for sustaining high levels of amylases from A. oryzae

``` an example of a traditional fermentation product that relies on a mix of yeast, mold, LAB and AAB is a) Kefir b) Kombucha c) Sake D) Fukuyama pot vinegar E) Camembert cheese ```

a beer that has undergone a very low apparent attenuation will taste: a) dry b) dark c) sweet d) slightly acidic e) like hops

is applying consistent moisture to hope necessary?

CO2 is more soluble at (higher/lower) temperatures

lower

sulfur dioxide is not: a) widely used in the food industry b) able to rapidly dissociate into bisulfite and sulfite in cells c) able to inhibit the growth of microorganisms d) able to degrade the cellular membrane of AAB e) able to rapidly kill wild yeast

both heterofermentative and homofermentative LAB can produce diacetyl (true or false)

true

AAB results in the oxidation of EtOH to acetic acid, producing odors and off flavors for wine

true

why do you add a single campden crush tablet to your wine preparation?

kill off wild yeast, dechlorinate, and act as an antioxidant

name 2 fermented products that make use of an airlock

sauerkraut, wine, cider

LAB are used in dairy fermentations because they are very proteolytic. from the perspective of LAB, why is proteolysis essential to their survival and proliferation?

lack systems to produce their own amino acids so they must obtain them externally. their enzymes enable the breakdown of many proteins, providing a wider range of amino acids available to them

why is C. botulinum not a concern in your sauerkraut production?

salt content + acidity from LAB

define selective media

allow certain types of organisms to grow, and inhibit the growth of other organisms.

define back slopping

adding in a portion of a previously successful fermentation to start a new one

define surface static process

AAB fermentation; forms cellulose raft on surface to maintain access to O2.

define nata de coco

made from komagataeibacter (AAB) on the surface of coconut water

define homofermentative lactic acid bacteria

produce 2 mol of lactic acid per mole of glucose via glycolysis

define gravity (as applied to alcohol fermentations)

specific gravity is the gravity relative to water. used to monitor the fermentation as the breakdown of sugars into ethanol results in a lower SG

define coagulation

the disruption of micelle structure in milk to cause protein insolubility and aggregation, forming clumps

define kefir

dairy fermented drink made with yeast and LAB

attenuation

measure of how complete the alcohol ferment is (beer); lower attenuation = less alcohol but more sugar

overoxidation

ability for AAB to oxidize acetic acid using the TCA cycle. may also occur with other organic acids

what's koji?

Aspergillus oryzae; mold; used in sake production

why is koji the mold of choice for any fermentation that requires the breakdown of starch. name one fermented food product that requires koji for its production

- most microbes can't make use of starch - koji has amylases to break down starch into simpler sugars - has a variety of enzymes to attack a variety of bonds, widening the range of starches that can be used as substrate - sake: used to break down rice, then LAB & yeast grow to outcompete spoilage microbes. the yeast produces alcohol - koji doesn't coexist with yeast and LAB

are LAB amino acid auxotrophs?

yeah

the most common type of microorganism that participates in the fermentation that produces kimchi is:

LAB

the most common organism that participates in the fermentation that produces wine is:

yeEEEEEeeeast

the microorganism that breaks down sugars during the production of sake is

mold

the microorganism that is responsible for rind formation on the surface of ripened cheeses is

mold

globally, most vinegar is produced by _____ sp. using an oxidative fermentation reaction a) acetobacter b) gluconobacter c) gluconacetobacter d) komagataeibacter

Where can you get a potentially novel acetic acid bacteria? a) surface of grape b) commercial bottle of traditionally fermented vinegar c) soil d) wine bottling facility

ethanol is converted into what during oxidative fermentation, before being converted to acetic acid?

acetaldehyde

heterofermentative bacteria a) produce 2 moles of lactate for every one mole of glucose b) use the 6-PG/PK pathway to ferment glucose c) produce 2 ATP molecules for every one molecule of glucose d) use glycolysis to ferment glucose

an ascus has greater resistance to environmental conditions than stationary phase cells

true

an ascus has greater resistance to environmental conditions than stationary phase cells

true

of these, which are aerobic and anaerobic? AAB, LAB, yeast, mold

aerobic: mold and AAB anaerobic: LAB and yeastr